Process of manufacturing a medical use electrical lead

ABSTRACT

A process for manufacturing an electrical lead having one or more electrodes includes providing an elongate member having at least one polymeric region and further having at least one electrical conductor that extends along at least a part of a length of the elongate member and that is contained in a wall of the elongate member. A length of the at least one electrical conductor is accessed at the at least one polymeric region. An electrically conductive adhesive is applied to the length of the at least one electrical conductor that has been accessed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. §371of International Application No. PCT/AU2005/000834, filed Jun. 10, 2005,which claims priority from U.S. Provisional Patent Application No60/599,651, filed Aug. 5, 2004, and 60/648,232, filed Jan. 28, 2005, thecontents of each of which are incorporated herein by reference in theirentirety.

FIELD

This invention relates to the manufacture of an electrical lead and,more particularly, to a process for manufacturing an electrical lead,such as an electrically conductive catheter, and to an electrical lead.

BACKGROUND

The electrical activity of the muscles in the heart directs the overallactivity of the heart. Many heart malfunctions, particularlyarrhythmias, are evidenced by or caused by electrical activity that isnot suitable for the heart's normal functioning. The electrical leadsdescribed herein are useful in the detection of the heart's electricalactivities and in its treatment by stimulation, ablation anddefibrillation.

Electrical leads having electrode regions have been used in the medicalfield for applications such as those referred to above.

Traditionally, the electrodes have been made from machined metal orcoiled wire components which, while having the requisite electricalconductivity, fail to provide the desired degree of flexibility requiredin a medical application.

Although the use of metal coated or metal filled polymers as medicalelectrodes has been considered, the amount of metal required to obtain asuitable level of conductivity renders the resultant lead stiff and notparticularly suitable for implantation into a patient.

SUMMARY

According to a first aspect of the invention, there is provided aprocess for manufacturing an electrical lead having one or moreelectrodes, the process including:

providing an elongate member having at least one polymeric region andfurther having at least one electrical conductor that extends along atleast a part of a length of the elongate member and that is contained ina wall of the elongate member;

accessing a length of the at least one electrical conductor at the atleast one polymeric region; and

applying an electrically conductive adhesive to the length of the atleast one electrical conductor that has been accessed.

One or more discrete electrodes may be formed along a length of theelongate member. The electrodes may comprise bands that extend at leastpartially around the circumference of the elongate member.

The electrically conductive adhesive may comprise any of a variety ofmaterials ranging from inherently conductive adhesives, adhesive basescontaining solid conductive fillers, adhesive bases containing dissolvedconductive materials, and mixtures of these materials. Adhesive basescomprising curable or settable polymeric materials, e.g., polymers thatare not tacky or sticky after curing or setting, are also suitable forthis purpose. Epoxies containing particulate or fibrillar metals aresuitable choices, particularly highly conductive, biocompatible metalssuch as silver, gold, platinum, palladium, rhodium, and their mixturesas well as alloys containing those metals and constructs of those metalshaving regions of differing composition. One choice may comprise asilver filled epoxy.

A further step of applying at least one electrically conductive materialto the electrically conductive adhesive may be carried out. Again, theelectrically conductive material may be any of a variety of materialsbut particularly suitable are those that are able to form a conductivelayer between the conductive adhesive and any additional material placedexternally to the at least one electrically conductive material.

One appropriate class of such electrically conductive materials, thosethat are to be applied to the adhesive, may be a class of liquidcarriers, particularly volatile carriers such as solvents, variouslycontaining solvated or complexed conductors or containing solidconductors. A subclass of these materials may be inks containingparticulate conductive metals, alloys or constructs such as silver orsilver coated with a metal such as platinum or palladium.

The electrically conductive adhesive or the electrically conductivematerial applied to the electrically conductive adhesive may be furtheroverlaid with a conductive metal such as those described above. Themetal may comprise platinum.

The elongate member may include a plurality of electrical conductors andthe process may include accessing a length of each of a plurality of theelectrical conductors at circumferentially spaced intervals about theelongate member and applying a pad of the electrically conductiveadhesive to the accessed length of each electrical conductor.

The process may include applying a layer of at least one electricallyconductive material to each pad of electrically conductive adhesive.Further, the process may include overlaying each pad of electricallyconductive adhesive with a metal layer including platinum or palladium.

The pads of electrically conductive adhesive may be arranged inlongitudinally aligned relationship about the circumference of theelongate member and the process may include applying the metal layerabout the circumference of the elongate member as a continuous layerand, thereafter, separating the layer into a plurality of electricallyisolated segments, for example, by laser cutting, arranged atcircumferentially spaced intervals to form a plurality of discreteelectrodes arranged about the circumference of the elongate member.

The process may include applying the metal including platinum bymounting a ring over the elongate member and securing the ring inposition. The ring may be secured by adhesive, crimping, or the like.

The electrical lead may include a number of conductors that extend alongat least a part of a length of the electrical lead. Although one or moreconductors may be specifically associated with an electrode, theelectrical lead may include further conductors that form part of atemperature sensing member. A temperature sensing member may beassociated with an electrode in such a way that it determines thetemperature at the electrode. To determine the temperature at theelectrode, the temperature sensing member may be electrically isolatedfrom a corresponding electrode.

The process may, therefore, include the further step of isolating anelectrical contact of the electrical lead from the one or moreelectrodes. The electrical contact may be isolated by:

accessing the electrical contact;

applying an electrically conductive adhesive to the first electricalcontact; and

electrochemically treating the electrically conductive adhesive suchthat a portion of the electrically conductive adhesive is converted toan electrically non-conductive portion.

The electrochemical treatment may include a step of passing a currentthrough the electrical contact such that a current also passes throughthe electrically conductive adhesive while the electrically conductiveadhesive is in an ionic environment containing a material tending toform an insulator (or high resistance layer) with some component of theelectrical contact. An ionic environment comprising a saline (NaCl)solution or potassium chloride solution may be suitable, although othersuch materials are envisaged.

Such a step converts a metal in the electrically conductive adhesiveelectrochemically to a metal chloride. Where the electrically conductiveadhesive comprises a silver filled epoxy, the silver situated onsurfaces facing the solution surface is converted to silver chloride.That silver chloride layer may act as an insulating layer.

The electrical contact may comprise a part of a temperature sensingmember such as a thermocouple.

According to a second aspect of the invention, there is provided aprocess of electrically isolating a first electrical contact of anelectrical lead from a second electrical contact of the electrical lead,the process including:

accessing the first electrical contact;

applying an electrically conductive adhesive to the first electricalcontact; and

electrochemically treating the electrically conductive adhesive suchthat a portion of the electrically conductive adhesive is converted toan electrically non-conductive portion.

The electrochemical treatment may comprise the step of passing a currentthrough the electrical contact and, hence, through the electricallyconductive adhesive to form an insulator. Similarly to the step above,the step may be practiced in an ionic environment containing a reactivematerial to produce an insulator or highly resistive material. In theinstance where silver-containing materials are chosen, a saline (NaCl)solution or potassium chloride solution may be suitable.

The electrically conductive adhesive may comprise those listed above,including silver filled adhesives such as a silver filled epoxy. Again,if so chosen, the silver in the portion of the adhesive may be convertedto silver chloride (AgCl) using the electrochemical reaction stepdiscussed above. The silver chloride formed is electricallynon-conductive.

The first electrical contact may comprise a temperature sensing member.

The second electrical contact may comprise an energy transmittingelectrode. The electrode may transmit energy, which creates heat in thetissue against which the electrode is placed in use.

The temperature sensing member may be in thermal contact with the energytransmitting electrode.

The temperature sensing member in this variation and others describedherein may comprise a thermocouple or other temperature sensing devicessuch as resistance temperature detectors (RTDs), thermistors, or ICdevices where the output of frequency or period is related to thetemperature. If a thermocouple is chosen, an appropriate choice ofconductors may comprise a first wire made of copper and a second wiremade of Constantan.

The electrical lead may comprise an elongate member wherein the wires ofthe thermocouple extend along at least a part of a length of theelongate member and may be contained in a wall of the elongate member. Ajunction may be formed between the two wires of the thermocouple inproximity to the electrode to form a closed loop thermocouple by theapplication of the electrically conductive adhesive to the wires tobring the wires into electrical connection with each other at thejunction.

At least one electrically conductive material may be applied over theelectrode and the thermocouple junction.

Broadly, according to a third aspect of the invention, there is provideda process of manufacturing an electrical lead, the process including:

providing an elongate member having a proximal end and a distal end, atleast one electrical conductor contained in the elongate member andextending from the proximal end toward the distal end of the elongatemember, the at least one electrical conductor terminating in electricalconnection with an electrically conductive zone arranged externally ofthe elongate member;

cutting the elongate member distally of the electrically conductivezone;

forming a non-conductive termination distally of the electricallyconductive zone; and

applying a conductive material over the electrically conductive zone andthe termination to form an end electrode of the electrical lead.

More specifically, according to the third aspect of the invention, thereis provided a process of manufacturing an electrical lead, the processincluding:

providing an elongate member having a proximal end and a distal end, theelongate member having one or more polymeric regions and further havinga plurality of electrical conductors that extend along at least a partof a length of the elongate member toward the distal end of the elongatemember, the electrical conductors being contained within a wall of theelongate member;

in respect of each of at least some of the electrical conductors,forming an electrically conductive zone in electrical contact with itsassociated electrical conductor by:

-   -   accessing a length of each of the at least some electrical        conductors through the polymeric region of the elongate member        and applying an electrically conductive adhesive to each        accessed electrical conductor;    -   applying conductive material at an access point associated with        each electrical conductor to form a plurality of longitudinally        spaced electrically conductive zones along the length of the        elongate member;

cutting the elongate member distally of one of the electricallyconductive zones;

applying an electrically non-conductive termination distally of the oneelectrically conductive zone; and

applying an electrically conductive material to bridge the electricallyconductive zone and the termination to form an end electrode of theelongate member.

The termination may be applied in a liquid state. The termination may beapplied in two stages.

Thus, a first layer may be applied to seal the distal end of theelongate member. A second layer may be applied and shaped to provide adesired shape to the end electrode.

The termination may be made from a suitable non-conductive materialincluding a resin. The termination may, particularly, be a syntheticresin such as an epoxy resin.

Instead, the termination may be a solid element which is adhesivelysecured to the distal end of the elongate member both to seal the endand to form the desired shape of the end electrode.

The desired shape may be a substantially dome shape.

The electrically conductive material may be any of a variety ofmaterials. Preferably, the electrically conductive material is appliedin two stages. Firstly, a first layer of an electrically conductivematerial may be applied in a liquid form. The liquid form may be aliquid carrier, particularly, volatile carriers such as solvents, theliquid carrier containing solvated or complexed conductive elements orcontaining solid conductive elements. A subclass of these materials maybe inks containing particulate conductive metals, alloys, or constructssuch as silver.

As indicated above, the first layer may be applied to the electricallynon-conductive termination and to the electrically conductive zonebridging the electrically conductive zone and the termination. Thiselectrically conductive layer may be applied by any suitable meansincluding brushing, dipping, pad printing, or the like.

The layer may be further overlaid with a conductive, biocompatiblematerial such as a suitable metal, for example, platinum.

According to a fourth aspect of the invention, there is provided anelectrical lead that includes:

an elongate member having a proximal end and a distal end, at least oneelectrical conductor contained in the elongate member and extending fromthe proximal end toward the distal end of the elongate member, the atleast one electrical conductor terminating in an electrically conductivezone arranged externally of the elongate member;

a non-conductive termination arranged distally of the electricallyconductive zone and at a distal end of the elongate member; and

at least one layer of an electrically conductive material bridging theelectrically conductive zone and the non-conductive termination to forman end electrode of the electrically conductive material.

According to a fifth aspect of the invention, there is provided aprocess of manufacturing an electrical lead, the process including:

providing an elongate member having a proximal end and a distal end, atleast one electrical conductor contained in the elongate member andextending from the proximal end toward the distal end of the elongatemember, the at least one electrical conductor terminating in electricalconnection with an electrically conductive zone arranged externally ofthe elongate member;

forming an access point in the elongate member to provide access to theat least one electrical conductor;

applying a radio opaque material to a region of the elongate memberlongitudinally in register with the access point but out of electricalcontact with the access point; and

forming the electrically conductive zone by applying at least one layerof an electrically conductive material about the elongate member to bein electrical contact with the conductor through the access point and tooverlie the radio opaque material.

According a sixth aspect of the invention, there is provided anelectrical lead that includes:

an elongate member having a proximal end and a distal end, at least oneelectrical conductor contained in the elongate member and extending fromthe proximal end toward the distal end of the elongate member;

an access point formed at a predetermined location in a wall of theelongate member to provide access to the electrical conductor;

a zone of radio opaque material carried by the elongate member in aregion of the elongate member longitudinally in alignment with theaccess point but circumferentially spaced from the access point; and

at least one layer of an electrically conductive material carried at thepredetermined location of the elongate member to provide electricalcontact with the electrical conductor through the access point and tooverlie the radio opaque material.

The access point may be in the form of a slit arranged transversely in awall of the elongate member. In this regard, the elongate member may bein the form of a tubular member with a plurality of electricalconductors helically wound, and embedded in, the wall of the elongatemember. Therefore, the slit may follow the direction of winding of theelectrical conductors.

In one embodiment of this aspect of the invention, the radio opaquematerial may be a layer of radio opaque material applied to an externalsurface of the elongate member to form a cuff about the elongate member.The cuff may be in a diametrically opposed position to the access pointon the elongate member. The radio opaque material may be applied by padprinting.

Thereafter, the process may include applying the layer of electricallyconductive material. The layer of electrically conductive material maycomprise a first layer, such as the silver ink referred to above.Thereafter, the first layer may be overlaid with a second,biocompatible, electrically conductive material such as platinum.

In another embodiment of this aspect of the invention, the radio opaquematerial may be inserted into a recess formed in the elongate member.The recess may be formed in a region of the elongate memberdiametrically opposed to the access point. The recess may be of anysuitable shape such as, for example, a slot, a cruciform shape, acircle, or the like. In this embodiment, the conductive layer, may, onceagain, be applied in two stages. These layers may be applied by padprinting.

The radio opaque material may comprise approximately 70% to 80%non-conductive material and about 20% to 30% of adhesive material.

The adhesive material may comprise an epoxy. Preferably, the epoxy ofthe radio opaque material is matched to that of the silver ink tofacilitate pad printing.

In the case where the radio opaque material is contained within a recessin the elongate member, the epoxy of the radio opaque material may beselected to be the same as that used in filling the access point. Thisis advantageous for biocompatibility purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, schematically, a partially sectioned side view of anelectrical lead in accordance with an embodiment of the invention;

FIGS. 2 a through 2 f show, schematically, steps of a process, inaccordance with an embodiment of the invention, for manufacturing theelectrical lead of FIG. 1;

FIG. 3 shows, schematically, the electrical lead after completion of theprocess;

FIG. 4 shows a schematic, sectional end view of an electrical leadmanufactured in accordance with a process of another embodiment of theinvention;

FIG. 5 shows a schematic, side view of a part of an electrical leadmanufactured in accordance with a process of yet another embodiment ofthe invention;

FIGS. 6 a through 6 d show, schematically, steps of a process, inaccordance with a further embodiment of the invention, of electricallyisolating a first electrical contact of an electrical lead from a secondelectrical contact of the electrical lead;

FIGS. 7 a through 7 e show, schematically, steps of a process, inaccordance with yet a further embodiment of the invention, formanufacturing an electrical lead;

FIG. 8 shows, schematically, a perspective view of an initial step of aprocess, in accordance with still a further embodiment of the invention,for manufacturing an electrical lead;

FIG. 9 shows a schematic, sectional end view of a first example of anelectrical lead manufactured in accordance with the still furtherprocess of manufacturing an electrical lead;

FIG. 10 shows a schematic, sectional end view of a second example of anelectrical lead manufactured in accordance with the still furtherprocess of manufacturing an electrical lead; and

FIGS. 11 a through 11 d show, schematically, variations of the exampleof the electrical lead shown in FIG. 9.

DETAILED DESCRIPTION

Referring to the drawings, an electrical lead made in accordance with aprocess for manufacturing an electrical lead, in accordance with anembodiment of the invention, is generally designated by the referencenumeral 10.

The electrical lead 10 comprises an elongate member 10 a carrying atleast one electrode 11 and, preferably, a number of band electrodes 11positioned at longitudinally spaced intervals along the length of theelongate member 10 a. An electrode not in the shape of a band is shownas 11 b.

FIG. 3 shows a side view of the resulting electrical lead 10 functioningas an electrode sheath of a catheter and extending from an introducer 30or a similar device. The lead 10 includes a plurality of longitudinallyspaced electrodes 11, at least some of the electrodes 11 being bandelectrodes

As described in the preceding paragraph, the electrical lead 10 is usedas the electrode sheath of a cardiac catheter. The electrodes 11 areused as “sensing electrodes” to sense electrical activity (whethernormal or not) in the muscles of the heart. In addition, the electrodes11 may be used to ablate an area of tissue in the heart to correct someanomaly.

Thus, each electrode 11 may initially be operable as a sensingelectrode. Such an electrode 11 enables a clinician to identify an areaof electrical disturbance in the heart of a patient. The electricaldisturbance may be caused by a damaged area of heart tissue that is“mis-firing.” Once located, the same electrode 11 may be switched to anablation function to ablate the damaged tissue.

Multi-function electrodes 11 may be particularly useful in the treatmentof atrial fibrillation. Atrial fibrillation, a cardiac arrhythmia,results when an area of cardiac tissue near the atrium “misfires.” Suchmisfiring causes an electrical disturbance in the normal electricalpathway and in the resultant pulsatile contraction of the atrium. Theresult is that the atrium contracts in a fast and disorganized manner.If the fibrillation is prolonged, the blood in the atrium is not fullyemptied into the ventricle leading to a number of complications. Bysensing the area of tissue that is causing the electrical disturbance,the precise area may then be ablated.

Production of the electrical lead 10 is shown in FIGS. 2 a through 2 f.Initially, as shown in FIG. 2 a, an inner member 12 made from a suitablepolymer such as polyethylene or polyether block amide (PEBAX) isprovided. Other polymeric materials are also acceptable and easilyidentified from the art.

As shown in FIG. 2 b, a plurality of conductors 13 is coiled in ahelical manner around an outer surface of the inner member 12.Alternatively, the conductors 13 are housed within a lumen of the innermember 12. Up to twenty-four, or more, conductors 13 may be used in theelectrical lead 10 and are either helically wound around or are situatedwithin the lumen of the inner member 12.

The conductors 13 are metal wires. The metal wires are insulated with apolymeric material such as nylon, polyurethane or a nylon-polyurethaneco-polymer. Examples of suitable conductors include copper or Constantancoated with a nylon-polyurethane blend.

As shown in FIG. 2 c, an outer polymeric jacket 14 is formed, forexample, by extrusion, over the inner member 12 and the conductors 13 toform the elongate member 10 a. The outer polymeric jacket 14 is madefrom materials similar to or the same as the materials of the innermember 12. Other materials may be selected as a matter of design choice,however.

The elongate member 10 a comprising the inner member 12, the conductors13 and the outer polymeric jacket 14 is heat treated to secure the outerpolymeric jacket 14 to the inner member 12 and to the conductors 13. Itwill be appreciated that a wall of the electrical lead 10 is thereforeeffectively made up of an inner layer defined by the inner member 12, acentral layer made up of the helically wound conductors 13 and an outerlayer defined by the outer polymeric jacket 14. The conductors 13 are,in effect, embedded in the wall and, as there is little, if any,polymeric material between adjacent turns of the conductors 13, there isthe ability for limited movement between adjacent turns, therebyimproving the flexibility of the electrical lead 10.

As shown in FIG. 2 d, a desired length of one or more conductors 13 isaccessed or exposed by laser cutting a portion of the outer polymericjacket 14. Laser cutting is accurate and provides a suitable way ofremoving a portion 32 of the outer polymeric jacket 14 with ease toproduce an opening 34. The area of the opening 34 of the outer polymericjacket 14 that has been removed is of a width similar to the width ofthe exposed conductors 13 and of a selected length extending along apredetermined length of the conductors 13, following the coiled orhelical path of the conductors 13. The amount of outer polymeric jacket14 that is removed largely depends upon the requirements of the finalelectrode 11. For example, there may be instances where it is desired toexpose two or more adjacent conductors 13 to provide an electrode 11with increased electrical conductivity and increased mechanicalstrength.

If the conductors 13 are insulated, the step of exposing theconductor(s) also comprises cutting and remvoing the layer of insulationover the wires in addition to cutting and removing a correspondingportion of the outer polymeric jacket 14.

As shown in FIG. 2 e, the opening 34 formed in the outer polymericjacket 14 is substantially filled with an electrically conductiveadhesive 15 of the types discussed above, such as a silver filled epoxy.The conductors 13 coated with the electrically conductive adhesive 15provide sufficient electrical conductivity to act as an electrode 11.Such an electrode 11 has particular application as a sensing electrode.

However, as shown in FIG. 2 f, the process, preferably, furthercomprises a step of covering the electrically conductive adhesive 15with a solvent that contains one or more conductive materials. The classof suitable materials is discussed above. These materials may be appliedin a variety of ways, e.g., spraying, electrostatic deposition, directapplication as by brush or pad, or the like. Good results are obtainedusing pad printing with silver filled ink or palladium filled ink or apalladium/silver ink 16.

Electrodes 11 formed in this manner, by pad printing an electricallyconductive adhesive 15 with an electrically conductive ink 16, have aparticular application as sensing electrodes. The process also includesa further step of catalyzing the pad printed ink 16 with an acidicpalladium chloride solution to deposit a coating of palladium on thesilver of the electrode.

The electrically conductive adhesive 15 or the pad printed coating ofink 16 is overlaid with a layer of platinum 17 to increase theelectrical conductivity across the electrode. An electrode 11 thatincludes a layer of platinum 17 is suitable for ablation in addition tosensing. The layer of platinum 17 is applied to the electrode 11 byelectroless plating but could also be applied by electrode depositiontechniques.

The final electrode 11 may also be coated with a layer of materialappropriate for prevention of metallic ions from the electrodes. Anepoxy layer may be applied by pad printing. The epoxy prevents themigration of silver ions from the electrode 11.

In FIG. 4 of the drawings where, with reference to previous drawings,like reference numerals refer to like parts unless otherwise specified,another embodiment of the invention is illustrated. In this embodiment,a plurality of the electrical conductors 13 are accessed throughexcising a plurality of the portions 32 (not shown in FIG. 4 but shownin FIG. 2 d) at circumferentially spaced intervals about the outerpolymeric jacket 14 to form a plurality of circumferentially spacedopenings 34. While FIG. 4 illustrates the openings 34 being inlongitudinal alignment, it will be appreciated that the openings 34could be staggered with respect to one another along the length of theouter polymeric jacket 14.

Each opening 34 is charged with the conductive adhesive 15 and the layer16 of electrically conductive material is pad printed about thecircumference of the outer polymeric jacket 14 overlying the conductiveadhesive 15 in each of the openings 34. The biocompatible metal layer 17is applied over the layer 16 of electrically conductive material.

Once the metal layer 17 has been applied, laser cuts 19 are made throughthe layers 16 and 17 to form a plurality of circumferentially spaceddiscrete electrodes 11. It will be appreciated that it is an advantageof this embodiment of the invention, that three-dimensional sensing orablating can be effected. Also, it is easier to place the electricallead 10, as the orientation of the electrodes 11 of the electrical lead10 relative to a site of a patient's body to be treated is lesscritical, as there is always likely to be at least one electrode 11 incontact with tissue.

Referring now to FIG. 5 of the drawings, yet a further embodiment of theinvention is described. Once again, with reference to the previousdrawings, like reference numerals refer to like parts unless otherwisespecified.

In this embodiment, instead of the layer 17 of each electrode 11 beingpad printed, a ring 60 is applied over the layer 16. The ring 60 issecured in position on the outer polymeric jacket 14 over its associatedlayer 16 by an appropriate securing technique, for example, an adhesive,crimping, being a press fit, or the like.

It is also useful to measure the temperature at an electrode 11,particularly in cases where the electrode 11 is used for ablationpurposes. The electrical lead 10, therefore, includes a thermocouple 20(FIG. 6 b) or other suitable temperature measuring component.

As shown in FIG. 6 a, in a variation including the thermocouple 20, thethermocouple 20 comprises a first wire 21 made from copper and a secondwire 22 made from Constantan. The outer polymeric jacket 14 is cut, forexample, by laser cutting, to expose the wires 21 and 22. Anelectrically conductive adhesive 15 is applied to the exposed wires asshown in FIG. 6 b. The electrically conductive adhesive 15 brings thetwo wires 21 and 22 of the thermocouple 20 into electrical contact witheach other thus providing a thermocouple junction 23.

When forming the thermocouple 20 in this way and to ensure accuratetemperature readings, the thermocouple 20 needs to be isolated from anassociated electrode 11 as described in the steps below. As shown inFIG. 6 c, after the wires 21 and 22 of the thermocouple 20 are exposedand the electrically conductive adhesive 15 has been applied to theexposed wires 21 and 22, the wires and adhesive are exposed to a saline(NaCl) solution 24 and a current is passed through the wires 21 and 22of the thermocouple 20 from a constant voltage source 26. The resultantcurrent passing through the adhesive 15 causes a metal in the adhesiveto convert to a metal chloride. When the adhesive 15 is a silver filledepoxy, the silver on an outer facing surface of the adhesive isconverted to a relatively thin layer 25 of silver chloride and acts as alayer of insulation, electrically isolating the thermocouple 20 from theelectrode 11 of the electrical lead 10.

As shown in FIG. 6 d, the adhesive 15 of the electrode 11 and theadhesive 15 of thermocouple 20 are then pad printed with a silver filledink 16 and a layer of platinum 17 is, optionally, applied to the ink 16.

The electrical lead 10 may comprise a single thermocouple 20 or,alternatively, a number of thermocouples. In the latter case, eachelectrode 11 formed on the electrical lead 10 may have a correspondingthermocouple 20.

EXAMPLE

A cable was sourced from Microhelix, Portland, Oreg. The cable had beenprepared by extruding a PEBAX jacket over a polymer coated wire mandrel.A mixture of nylon/polyurethane insulated copper and Constantan wires(each 0.125 mm) were helically coiled around the polymer coated wiremandrel at a controlled pitch/coiling angle. The PEBAX jacket was thenlaid over the coiled wires. The resultant cable was cut to length andthe mandrel removed. The cable was then heat treated to secure the outerPEBAX jacket to the coiled wires.

Excimer laser cut windows were then cut over the individual wires atpredetermined locations. The exact locations of the windows wereprogrammed into the laser. The outer PEBAX jacket over the individualwire, together with the insulation layer of the wire, was removedwithout disturbing the wire beneath.

The openings formed by removal of the regions of PEBAX and insulationwere filled with a silver filled epoxy from Creative Materials Inc.,Tyngsboro, Mass., using an air actuated dispenser. The silver filledepoxy was cured at a temperature of about 140° C. and subsequentlyplasma treated in an argon atmosphere for approximately 1 min.

The silver filled epoxy regions were then pad printed with a silverfilled ink. A plate with indentations relating to the size and spacingof the desired electrodes was wiped with the silver filled ink, leavingink behind in the indentations. A pad was then brought down over the topof the plate along the length of the ink filled wells. The pad picked upthe ink and was placed on the cable such that the inkpads correspondedwith the regions of epoxy on the cable to deposit the ink on the cableover the regions of epoxy. This step was repeated a number of times asthe cable was rotated such that a series of bands was formed around thecircumference of the cable.

The cable was then cured in an oven at about 140° C. for up to 15 hours.

The bands of the cable were then further catalyzed with an acidic PdClsolution.

Finally, the cable was placed in a commercially available electroless Ptsolution using hydrazine as the reducer for approximately 1 hour atabout 60° C. A layer of platinum approximately 0.5 micron in thicknesswas formed over the bands to form final band electrodes.

Referring to FIGS. 7 a through 7 e of the drawings, a further embodimentof a process for manufacturing an electrical lead 10 is described. Withreference to the previous drawings, like reference numerals refer tolike parts unless otherwise specified.

In this embodiment of the invention, the electrodes 11 are formed atspaced intervals along a length of the elongate member 10 a to be inelectrical communication with the underlying conductors 13 (not shown inFIGS. 7 a through 7 e).

The elongate member 10 a is cut at a distal end 40, as shown in FIG. 7 aof the drawings, distally of one of the electrodes 11.

A layer of an epoxy 42 is applied at the distal end 40 of the elongatemember 10 a to seal the distal end of the elongate member 10 a and toisolate the ends of the conductors 13 (not shown in FIGS. 7 a through 7e) at the distal end 40. A further bead of epoxy 44 is applied to thelayer 42 to form an end electrode of a required dome shape 46.

In a following step, the dome-shaped end 46 is coated with conductivesilver ink of the same formulation as that used in the formation of theelectrodes 11 as shown in FIG. 7 d of the drawings. It will therefore beappreciated that an end electrode 48 is formed prior to the applicationof the platinum layer 17 on the electrodes 11.

Therefore, once the dome-shaped end 46 has been coated with the silverink, all of the electrodes 11 and the end electrode 48 are coated with alayer of platinum 17 as shown in FIG. 7 e of the drawings. Once again,the platinum layer 17 is applied by electroless plating.

Referring now to FIGS. 8 through 11 of the drawings, yet a furtherprocess for manufacturing an electrical lead 10 is illustrated. Onceagain, with reference to the previous drawings, like reference numeralsrefer to like parts, unless otherwise specified.

In this embodiment, prior to the formation of the electrodes 11 aboutthe outer polymeric jacket 14, once each opening 34 has been formed inthe outer polymeric jacket 14, a radio opaque material 50 is appliedlongitudinally in register with each of at least some of the openings34.

In the case of the embodiment shown in FIGS. 8 and 9 of the drawings,the radio opaque material 50 is applied in the form of a cuff 52 about apart of the circumference of the outer polymeric jacket 14.

The cuff 52 is arranged on the outer polymeric jacket 14 so that it isat the same longitudinal position on the outer polymeric jacket 14 asits associated opening 34 but is arranged in diametrically opposedrelationship to the opening 34 so that the radio opaque material 50 isnot in electrical contact with the conductor 13 or the electricallyconductive adhesive 15 in the opening 34.

The radio opaque material 50 is applied by pad printing and comprisesbetween 70% to 80% non-conductive material and 20% to 30% adhesive. Theradio opaque material is a radio opaque ink sourced from CreativeMaterials Inc. of 141 Middlesex Road, Tyngsboro, Mass., 01879, UnitedStates of America. The adhesive part of the radio opaque material 50 is,conventionally, an epoxy. The epoxy of the radio opaque material 50 ismatched to the epoxy of the silver layer 16, which is advantageous forbiocompatibility purposes.

Once the radio opaque material 50 has been applied, the layer ofelectrically conductive silver material 16 is pad printed to overlie theradio opaque material 50 and the adhesive 15 in the opening 34.Thereafter, the platinum layer 17 is applied by electroless plating.

In the embodiment shown in FIGS. 10 and 11 of the drawings, instead ofapplying the radio opaque material 50 as a cuff 52, a recess 54 isformed in the outer polymeric jacket 14 in diametrically opposedrelationship to the opening 34. It will be appreciated that the recess54 is of such a depth that it does not expose any of the conductors 13in the outer polymeric jacket 14.

The radio opaque material 50 is charged into the recess 54. In thisembodiment, the epoxy of the radio opaque material 50 is selected to bethe same as the epoxy used to form the electrically conductive filling15 of the opening 34. Once again, this is advantageous forbiocompatibility purposes.

The recess 54 can be any suitable shape. Thus, as shown in FIG. 11 a ofthe drawings, the recess 54 may be a longitudinally extending slit.Instead, as shown in FIGS. 11 b and 11 c of the drawings, the recess 54could be of a cruciform shape. As shown in FIG. 11 d of the drawings,the recess could be a circular recess. It will be appreciated that anyother shape of recess could equally advantageously be employed.

Once the recess 54 contains the radio opaque material 50, the silver ink16 is applied by pad printing followed by the electroless plating of theelectrode 11 with a platinum layer 17.

It will be appreciated that the silver ink layer 16 or the platinumlayer 17 need not extend over the radio opaque material 50 or recess 54,as the case may be. It is only necessary that the radio opaque material50 or recess 54 be longitudinally aligned with its associated electrode11.

It is an advantage of this embodiment that a radio opaque region isformed in alignment with the electrode 11 allowing for rapid andaccurate placement of the electrode 11 by a clinician viewing theposition of the electrode 11 on a fluoroscope.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to this described processwithout departing from the spirit or scope of the broadly description.The specific descriptions are, therefore, to be considered in allrespects as illustrative and not restrictive.

1. A process for manufacturing a medical use electrical lead having oneor more electrodes, the process including: providing an elongate memberhaving at least one polymeric region and further having at least oneelectrical conductor that extends along at least a part of a length ofthe elongate member and that is contained in a wall of the elongatemember; accessing a length of the at least one electrical conductor atthe at least one polymeric region; and applying an electricallyconductive adhesive to the length of the at least one electricalconductor that has been accessed.
 2. The process of claim 1, wherein theelectrically conductive adhesive comprises a silver filled epoxy.
 3. Theprocess of claim 2, wherein at least some silver particles of the silverfilled epoxy are platinum-coated particles or palladium-coatedparticles.
 4. The process of claim 1, further including applying atleast one electrically conductive material to the electricallyconductive adhesive.
 5. The process of claim 1, further includingoverlaying the electrically conductive adhesive with a metal includingplatinum.
 6. The process of claim 4, further including overlaying theelectrically conductive material with a metal including platinum.
 7. Theprocess of claim 1, wherein the elongate member includes a plurality ofelectrical conductors, and wherein the process includes accessing alength of each of a plurality of the electrical conductors atcircumferentially spaced intervals about the elongate member andapplying a pad of the electrically conductive adhesive to the accessedlength of each electrical conductor.
 8. The process of claim 7, furtherincluding applying a layer of at least one electrically conductivematerial to each pad of electrically conductive adhesive.
 9. The processof claim 7, further including overlaying each pad of electricallyconductive adhesive with a metal layer including platinum or palladium.10. The process of claim 9, wherein the pads of electrically conductiveadhesive are arranged in longitudinally aligned relationship about thecircumference of the elongate member, and wherein the process furtherincludes applying the metal layer about the circumference of theelongate member as a continuous layer and, thereafter, separating thelayer into a plurality of electrically isolated segments arranged atcircumferentially spaced intervals to form a plurality of discreteelectrodes arranged about the circumference of the elongate member. 11.The process of claim 6, further including applying the metal includingplatinum by mounting a ring over the elongate member and securing thering in position.
 12. The process of claim 1, further includingisolating an electrical contact of the electrical lead from the one ormore electrodes by: accessing the electrical contact; applying anelectrically conductive adhesive to the electrical contact; andelectrochemically treating the electrically conductive adhesive suchthat a portion of the electrically conductive adhesive is converted toan electrically non-conductive portion.
 13. The process of claim 12,wherein electrochemically treating the electrically conductive materialcomprises passing a current through the electrical contact in an ionicenvironment.
 14. The process of claim 13, wherein the ionic environmentcomprises a saline (NaCl) solution to convert a metal in theelectrically conductive adhesive electrochemically to a metal chloride.15. The process of claim 12, wherein the electrical contact is a contactof a thermocouple junction.
 16. The process of claim 1, furthercomprising electrochemically treating the electrically conductiveadhesive such that a portion of the electrically conductive adhesive isconverted to an electrically non-conductive portion.
 17. The process ofclaim 16, wherein the electrochemical treatment comprises the step ofpassing a current through the electrical contact in an ionicenvironment.
 18. The process of claim 17, wherein the ionic environmentcomprises a saline (NaCl) solution to convert a metal in theelectrically conductive adhesive electrochemically to a metal chloride.19. The process of claim 16, wherein the first electrical contactcomprises a temperature sensing member.
 20. The process of claim 16,wherein the second electrical contact comprises an energy transmittingelectrode.
 21. The process of claim 20, wherein the temperature sensingmember comprises a thermocouple, the thermocouple having a first wiremade of copper and a second wire made of Constantan.
 22. The process ofclaim 16, further providing an elongate member having a proximal end anda distal end, at least one electrical conductor contained in theelongate member and extending from the proximal end toward the distalend of the elongate member, the at least one electrical conductorterminating in electrical connection with an electrically conductivezone arranged externally of the elongate member, wherein the processfurther includes: cutting the elongate member distally of theelectrically conductive zone; forming an electrically non-conductivetermination distally of the electrically conductive zone; and applyingan electrically conductive material over the electrically conductivezone and the electrically non-conductive termination to form an endelectrode of the electrical lead.
 23. The process of claim 1, whereinproviding the elongate member includes providing the elongate memberhaving a proximal end and a distal end, the elongate member having aplurality of polymeric regions and further having a plurality ofelectrical conductors that extend along at least a part of the length ofthe elongate member toward the distal end of the elongate member, theplurality of electrical conductors being contained within a wall of theelongate member, wherein the process further includes: in respect ofeach of at least some of the plurality of electrical conductors, formingan electrically conductive zone in electrical contact with itsassociated electrical conductor of the plurality of electricalconductors by: accessing a length of each of the at least someelectrical conductors of the plurality through the plurality ofpolymeric regions of the elongate member and applying an electricallyconductive adhesive to each accessed electrical conductor of theplurality; applying an electrically conductive material at an accesspoint associated with each electrical conductor of the plurality to forma plurality of longitudinally spaced electrically conductive zones alongthe length of the elongate member; cutting the elongate member distallyof one electrically conductive zone of the plurality; applying anelectrically non-conductive termination distally of the one electricallyconductive zone; and applying another electrically conductive materialto bridge the one electrically conductive zone and the electricallynon-conductive termination to form an end electrode of the elongatemember.
 24. The process of claim 22, further including applying theelectrically non-conductive termination in a liquid state.
 25. Theprocess of claim 24, further including applying the electricallynon-conductive termination in at least two stages, with a first layerbeing applied to seal the distal end of the elongate member and a secondlayer being applied and shaped to provide a desired shape to the endelectrode.
 26. The process of claim 22, further including applying asolid electrically non-conductive termination to the distal end of theelongate member.
 27. The process of claim 22, further including applyingthe electrically conductive material in at least two stages.
 28. Theprocess of claim 27, further including applying a first layer to theelectrically non-conductive termination and to the electricallyconductive zone bridging the electrically conductive zone and theelectrically non-conductive termination.
 29. The process of claim 28,further including overlaying the first layer with an electricallyconductive, biocompatible material.
 30. The process of claim 1, furtherincluding: applying a radio opaque material to a region of the elongatemember longitudinally in register with the at least one polymeric regionbut out of electrical contact with the at least one polymeric region;and forming an electrically conductive zone by applying at least onelayer of an electrically conductive material about the elongate memberto be in electrical contact with the at least one conductor through theat least one polymeric region and to overlie the radio opaque material.31. The process of claim 30, further including applying the radio opaquematerial as a layer to an external surface of the elongate member toform a cuff about the elongate member.
 32. The process of claim 31,further including positioning the cuff in a diametrically opposedposition to the at least one polymeric region on the elongate member.33. The process of claim 32, further including applying the at least onelayer of electrically conductive material over the cuff, the at leastone layer of electrically conductive material comprising a firstelectrically conductive layer overlaid with a second, biocompatible,electrically conductive material layer.
 34. The process of claim 30,further including inserting the radio opaque material into a recessformed in the elongate member, the recess being formed in a region ofthe elongate member diametrically opposed to the at least one polymericregion.
 35. The process of claim 10, further including applying themetal layer including platinum by mounting a ring over the elongatemember and securing the ring in position.
 36. The process of claim 23,further including applying the electrically non-conductive terminationin a liquid state.
 37. The process of claim 36, further includingapplying the electrically non-conductive termination in at least twostages, with a first layer being applied to seal the distal end of theelongate member and a second layer being applied and shaped to provide adesired shape to the end electrode.
 38. The process of claim 23, furtherincluding applying a solid electrically non-conductive termination tothe distal end of the elongate member.
 39. The process of claim 23,further including applying the electrically conductive material in atleast two stages.
 40. The process of claim 39, further includingapplying a first layer to the electrically non-conductive terminationand to the one electrically conductive zone bridging the oneelectrically conductive zone and the electrically non-conductivetermination.
 41. The process of claim 40, further including overlayingthe first layer with an electrically conductive, biocompatible material.42. The process of claim 1, wherein accessing a length of the at leastone electrical conductor at the at least one polymeric region furthercomprises cutting a portion of the wall of the elongate member.